Method of preventing alternating-current electrolysis.



J. L. R. HAYDEN. METHOD OF PREVENTING ALTERNATING CURRENT ELECTROLYSIS.

APPLICATION FILED JANA, 1907.

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JOSEPH L B. HAYDEN, OF BCHENECTADY, "NEW YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION 'OF NEW.YOBK.

METHOD OI PREVENTING ALTERNATING-CUBRENT ,ELEC'I BOL YSIS Patented Dec. 5, 1911.

Application filed January 4, 1907. Serial No. 850,852.

To all whom it may concern: I

Be it known that I, JOSEPH Ln Roy HAY DEN, a citizen of the United States, residing at Schenectady, county of Schenectady,

'State of New York, have invented certain new and useful Improvements in Methods of Preventin Alternating-Current Electrolysis, of w ich thefollowing is a specification.

My invention relates to a method of and apparatu'svfor preventing electrolysis of an a ternating current electrode immersed in an electrolyte, as in the case of iron pipes, lead covered cables and similar articles buried in the earth and subjected to the action of-an alternating current, such for example as leakage or stray current from an alternating current railway system. When such a pipe or cable buried in the" earth is made a part of an alternating current circuit the .positive half-wave of the current, during which current is flowing from the pipe orcable into the earth, tends to produce electrolytic corrosion .ofthe pipe or cable, while the negative half-wave immediately following, durin which current is flowing from the earth 1nto the pipe or cable, tends to reverse or neutralize .the electrolytic act-ion of the preceding positive half-wave. The negative alf-wave, however, does not entirely new tralize or overcome the efiect of'the posit-ive-half-wave, hence the cumulative action of the positive half-wavesresults in an electrolytic corrosion or wasting "away of the ipe or cable, and the object of my invention is to counteract and completely neutralize the difference between the effects of the positive half-wave and of the negative halfwave so as to completely protect the cable My invention in its broadest aspect comprises a method of overcoming electrolytic corrosion by alternating currents, which consists in causing a greater amount of energy to flow into the electrode to be protected than flows out of it, whereby the electrolytic corrosion, caused by the positive half-waves of the alternating current, is completely overcome or neutralized.

My invention also consists of superimposing upon the alternating current, uni-directional current continuously flowing into the electrode to be protected, thereby completely overcoming or neutralizing the electrolytic corrosion due to the difference between the positive and negative half-waves of the altional current,.the amount of uni-directional current ranging from just enough to neutrallze the excess effect of the ositive halfwvave overt-he negative hal -wave to. an amount great enough to so modify the alternating current that the electrode to be protected is always at a negative potential. My invention also comprises apparatus for carrying out this method, Whl'Ch consists essentially of means for making the negative half-wave of the alternating current enough greater than the positive halfwave to completely overcome and'neutralize the electrolytic corrosion produced by the positive half-wave; ofmeans for superimposing upon an alternating current a unidirectional current of a direction and intensity to overcome and" neutralize completely the electrolytic effect of the alternating current; of means for causing a uni- "vention; and Fig. 3 is a diagram showing the alternating current'with the uni-directional current superimposed thereon, the I light horizontal line showing the constant potential, and the dotted line showing the form of the waves of the resultant current.

One embodiment'of my invention is disclosed in Fig. 1 in which 1 and 2/represent an alternating current circuit which, through a transformer 3, supplies current to the trolley-wire 4 and rails 5 of a railway system. The car or locomotive 6, runnin upon the rails 5 takes current from the tro ley wire 4 by means of the trolley'Z. A pipe, lead covered cable, or similar article 8 is buried in the earth adjacent to the railway. It is found inpractice that when current is flowcurrent due to the diflerence of potential beto where the transformer 3 is connected to the rails, these stray currents being great enough to cause electrolysis of the pipe or cable, the earth acting as an electrolyte and the pipe or cable acting as an electrode in an alternating current circuit.

In carrying out my invention I so change the relation between the positive half-waves of the alternating current flowing between the pipe or cable 8 and the rails'5, that the negative half-waves, during which current is flowing into the cable or pipe 8, represent a greater amount-of energy than do the positive half-waves, during which current is flowing out of the pipe or cable 8 into the earth, whereby the electrolytic action of the positive half-waves is completely neutralized. One method of accomplishing this result is by superimposing upon the alternating current a small unidirectional-current flowing from the earth or ,the rails 5 into the pipe or cable 8. Any source of unidirectional current, such as a mercury rectifier 9; supplied by a transformer 10 connected between the trolley 4 and the rails 5 has its negative pole connected to the pipe or cable 8 by means of a lead 11. Any other source of unidirectional current, such as a motor generator set 14 or a battery could be substituted for'the rectifier as shown in Fig. 2 of the drawings. The negative pole of the rectifier is connected to the pipe or cable 8 through the lead 11, whilethe positive pole is connected to the rails 5 or to the ground by means of the lead 12, although either the connection to the rails 5 or the connection to the ground 13 may be omitted, either connection alone being sufficient to carry out my invention, while the negative pole of the motor generator set 14: maybe connected through the lead 15 to the pipe or cable 8 to secure the same result as when the rectifier 9 is used.

The result of the arrangement shown'in Figs. 1 and 2 is to cause the amount of energy of the waves flowing into the pipe or cable 8 to-be greaterthan that of the waves flowing out of it, this. result being secured by superimposing the small unidirectional tween the positive and negative poles of the source of unidirectional chrrent upon the alternating current flowing between the ipe or cable 8 and the rails 5. The result 0 superimposing the unidirectional current upon the alternating current is to make the negative half-wave larger than the positive halfwave, and' by properly proportioning the amount of unidirectional current .to the amount of alternating -=Lrrent, the electrolytic action of the alternating current can be completely counteracted and neutralized. It is found that a uni-directional current amounting to 1.5% of the stray alternating rent does no harm even though the stray alternating current is zero.

The alternating otential and current between the pipe an ground is measured in' any well-known manner at various points under varying conditions, and the uni-directional potential is kept higher at those points where the difierence of alternating potential between the pipe and ground is high than where it is low in order to make the uni-directional potential approximately proportional to the alternating potential which tends to produce a stray alternating current. The average amount of uni-directio'nal current at any particular point is approximately a predetermined percentage of the average alternating current at, that point, since the potential distribution in the ground in a railwa system varies'but little with the location 0 the individual cars, and any increase in stray current at any particular oint, due to a car passing that point, is sli ht and of very short duration.

y invention may be carried out in many other ways than that disclosed and described, and I therefore do not wishto be restricted to the particular disclosure contained in this specification, but intend to cover by the claims all changes and modifications which are within the spirit and scope of.m invention.

W at-I claim as new and desire to secure by Letters Patent of the United States, is,-

1 The method of reventing electrolysis of metal buried in the earth and forming part of an alternating current circuit through the earth which consists in causing a greater flow of energy in the alternating current circuit in a directionto prevent electrolysis of the metal than in the other direction.

2. The method of reventing electrolysis of metal buried in th part of an alternating current circuit through the earth which consists in causing more flow. of energy in the alternating current circuitduring the negative half wave 1 than during the positive half wave.

lbs

e earth and forming 0. The combination with a metal object buried in the earth and forming part of an alternating current circuit through the earth,

whereby said metal object is electrolytically corroded by the flow of current in said circuit, of means for causing the flow of energy in said circuit in a direction to prevent electrolysis of said metal to be greater than the flow in the other direction.

6. The combination with a metal object buried in the earth an dforming part of an alternating current circuit through the earth, whereby said metal object is electrolytically corroded by'the flow of current in said circuit, of means for causing unidirectional current to flow into said metal from the earth to counteract the electrolytic effect of the alternating current upon said metal.

7. The combination with a metal object buried in the earthand forming part of an alternating current circuit through the earth, whereby said metal object is electrolytically corroded by the flow of current in said circuit, of means for supplying unidirectional current between said metal and the earth and connections whereby said metal is made the cathode of a unidirectional current and thereby electrolysis is prevented.

8. The combination with a metal object buried in the earth to form part of an alternating current circuit through the earth,

whereby said metal object is electrolytically corroded by the flow of current in said cir-- cuit, of means for causing a greater amount of energy to flow into the metal from the earth during the negative half Wave of the alternating current than flows out of the metal during the positive half wave.

9. The combination with a conductor, an alternating current generator connected to said conductor and a metal object buried in the earth and forming part of the return circuit through the earth from said conductor to said generator, of a source of supply of unidirectional current between said metal object and the earth, and a connection between the negative pole of said source and said metal object for preventing electrolysis of said metaL.

10. The combination with a conductor, an alternating current generator connected to said conductor and a metal object buried in the earth and forming part of the return circuit through the earth from said conductor to saidgenerator, of a source of unidirectional current having its positive pole grounded in the earth and its negative pole connected to said metal object whereby unidirectional current is supplied between said metal object and the earth in a direction to prevent electrolysis of said metal.

In witness whereof, I have hereunto set my hand this 2nd day of J anuary, 1907.

JOSEPH L. R. HAYDEN.

Vitnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

